John Walko
EE Times Europe
02/28/2008 1:57 PM

LONDON — Cambridge Consultants claims it has come up with a solution to the acutely embarrassing technical challenge faced by the UK's Ministry of Defense over the potential interference of its radars from proposed energy wind farms.

Earlier this month it emerged that — much to the anger of energy companies trying to tap into the wind farm business — the MoD has objected on safety and security grounds to many of the proposed schemes that are within range of ground radar stations.

The Ministry has found problems when ground radar equipment is being used to distinguish the RAF's latest aircraft flying low at heights of some 250 ft from the ground and the rotating blades on 400ft high wind turbines.

The wind farms, it is said, are confusing the radar because its turbines are mistaken for planes. The rotating blades can mimic the effect of aircraft when detected by radio waves.

Cambridge Consultants (Cambridge, England) says it has come up with a low-cost solution to the conflict which involves adding advance radar sensors to off-shore turbines to eliminate blind spots.

Other proposed solutions to the problem include major reviews of radar technology and relocation of radar installations.

Solutions proposed have included the installation of new radar sensors in locations that do not have a direct view of the wind farm, such as in the lee of a ridge; modification of the turbines to minimize their effect; or new signal processing for the surveillance radar to reduce their susceptibility to clutter.

Cambridge Consultants notes the first of these depends on the availability of a suitable location, which often is too remote. The second will add significant cost and complexity to the wind farm, while the third is a fundamental technical challenge for radar equipment optimized for the longest detection range. It adds any solution would have to be adapted for each of the various types of radar in use.

BAE Systems has already been awarded a contract by the Ministry to try and find a way of mitigating the impact of the wind turbines on military and potentially civilian air traffic control radars. The answer could be a software program that can filter out the rotating blades.

According to Dr Gordon Oswald, technology director at Cambridge Consultants: "The issue particularly affects large off-shore wind turbine arrays, whose echoes can create a radar blind spot. Echoes from the wind farm can yield false alarms, and it is harder to identify flying objects within the shadowed zone."

The proposed solution, based on the company's holographic radar technology, has been developed and deployed across a range of applications including ice penetration, automotive and through-wall surveillance equipment. Fill-in radar sensors would be sited at the wind farms themselves to cover the shadowed zone.

They will be capable of eliminating the gaps and erroneous signals in air- traffic-control and other surveillance radar coverage caused by wind turbine blades.

The company says this approach is a major enhancement of much shorter-range tactical radars such as prism200, designed to cope with a cluttered through-wall scenario. It will reduce the complexity and cost of the required radar sensors, making the system an affordable component of a wind farm installation.

Dr Oswald stresses the solution would be extremely cost-effective, especially in view of the cost of losing available wind energy, or even the public enquiries which stem from the process of developing new wind turbine sites.

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